I think this is more about storing the entire repository on s3, not just large files as git-lfs and git-annex are usually concerned with. But coincidentally, git-annex somewhat recently got the feature to use any of its special remotes as normal git remotes (https://git-annex.branchable.com/git-remote-annex/), including s3, webdav, anything that rclone supports, and a few more.